The present invention generally relates to a technology for controlling access to files by using a file control list.
Generally, a file server (for example, NAS (Network Attached Storage)) is used in order to share files between a plurality of clients (users). Access to the shared files is controlled using an access control list (‘ACL’ hereinbelow). The ACL describes which users are able to access files in which operations, for example.
Representative examples of ACL include POSIX ACL, which is used by UNIX (registered trademark), and NTFS ACL, which is employed by Windows (registered trademark). The POSIX is an abbreviation for Portable Operating System Interface and NTFS is an abbreviation for NT FileSystem. Although there are a lot of file servers compatible with only POSIX ACL, there are also file servers that are compatible with NTFS ACL.
POSIX ACL and NTFS ACL are not directly interchangeable. As a result, in order to perform access control using NTFS ACL, it is necessary to switch the file system from a file system of a type which corresponds with POSIX ACL to a file system of a type that corresponds with NTFS ACL. More specifically, for example, it is necessary to temporarily stop services (stop accepting file access requests from the client, for example) and, while services are stopped, generate and associate, for each file, NTFS ACL which correspond with the file system following the switch using the procedure disclosed by Japanese Application Laid Open No. 2005-78612, for example.
In general, the number of files stored in a storage device is huge. For this reason, when the generation of ACL which corresponds with the file system of the type following the switch is performed for all files, the length of time services are stopped increases. The length of service stoppage time is desirably as short as possible and ideally zero.